Bilingualism is a long-term cognitively challenging experience that modulates metabolite concentrations in the healthy brain

Christos Pliatsikas,T Voits,V Deluca,J Rothman,S M Pereira Soares

doi:10.1038/s41598-021-86443-4

Christos Pliatsikas, T Voits + Show 3 more

Open Access

https://doi.org/10.1038/s41598-021-86443-4

Copy DOI

Abstract

Cognitively demanding experiences, including complex skill acquisition and processing, have been shown to induce brain adaptations, at least at the macroscopic level, e.g. on brain volume and/or functional connectivity. However, the neurobiological bases of these adaptations, including at the cellular level, are unclear and understudied. Here we use bilingualism as a case study to investigate the metabolic correlates of experience-based brain adaptations. We employ Magnetic Resonance Spectroscopy to measure metabolite concentrations in the basal ganglia, a region critical to language control which is reshaped by bilingualism. Our results show increased myo-Inositol and decreased N-acetyl aspartate concentrations in bilinguals compared to monolinguals. Both metabolites are linked to synaptic pruning, a process underlying experience-based brain restructuring. Interestingly, both concentrations correlate with relative amount of bilingual engagement. This suggests that degree of long-term cognitive experiences matters at the level of metabolic concentrations, which might accompany, if not drive, macroscopic brain adaptations.

Highlights

Demanding experiences, including complex skill acquisition and processing, have been shown to induce brain adaptations, at least at the macroscopic level, e.g. on brain volume and/or functional connectivity
This study suggests that there might be effects of bilingualism on brain metabolism that are not detectable behaviourally, echoing some evidence in the neuroimaging literature suggesting that behavioural measures might not always capture latent effects of bilingualism on brain function[37]
Building on findings that the cognitively challenging experience of bilingualism can have knock-on consequences for the structure and function of brain regions related to language acquisition and control, and the connectivity between t hem[6,30,45], the present study used MRS to investigate metabolic correlates of these adaptations

Summary

Introduction

Demanding experiences, including complex skill acquisition and processing, have been shown to induce brain adaptations, at least at the macroscopic level, e.g. on brain volume and/or functional connectivity. Our results show increased myo-Inositol and decreased N-acetyl aspartate concentrations in bilinguals compared to monolinguals Both metabolites are linked to synaptic pruning, a process underlying experience-based brain restructuring. Both concentrations correlate with relative amount of bilingual engagement. Grey and white matter adaptations have been reported for cognitively demanding experiences such as learning a new language, mastering complex visuospatial tasks and memory training[3,4,5]. Volumetric changes in grey matter structure have been interpreted as a mechanism that temporarily increases the availability of neural pathways for a new skill to be acquired, most likely via the generation of new dendritic spines This is subsequently followed by pruning of idle connections and spines while retaining the most efficient networks. These include: N-acetylaspartate (NAA), a marker of neural density and viability, Choline (CHO), related to the density and integrity of the cell membrane, Creatine (CRE), considered essential in cellular energy metabolism, Glutamate + Glutamine (GLX), which play a role in detoxification and regulation of neurotransmitters, and myo-Inositol (INS), a marker of glial proliferation and glial size (for review, s ee[7])

Methods

Results

Conclusion